The present invention relates generally to an apparatus and a method for separating sanitary effluent from storm water and/or infiltrated water in a municipal sewer system.
Municipal sewer systems include a web of pipes that convey wastewater from homes, businesses and industries and storm water from drains to treatment plants. The smallest pipes, typically twelve inches in diameter or less, are know as “collectors” that are connected to service lines running to the sanitary plumbing of buildings. The collectors are connected to “trunk lines”, typically larger than twelve inches in diameter, and carrying one to ten million gallons per day. The trunk lines connect to “interceptors” that carry the wastewater to a treatment plant. The interceptors are of large diameter, often more than ten feet.
The wastewater plumbing system in a typical house, office building or manufacturing facility combines toilet effluent with other wastewater, such as from sink and bath drains, to be carried by a single service line to the collector line at the street. Hereinafter, such combined wastewater will be termed “sanitary effluent”. Some municipal sewer systems combine and carry in the same pipes the sanitary effluent from buildings, storm water from outside drains and any ground water leaking into the system (infiltrated water). Other municipal systems combine and carry in the same lines sanitary effluent from buildings, infiltrated water, and water from downspouts and/or footing drains, while having a separate storm drain system, but which in any case the two systems are interconnected downstream. When the treatment plant and the associated web of pipes are built, the system is sized to process a predetermined number of gallons per unit of time, the maximum flow capacity, including a certain rainfall amount. As additional buildings are connected to the system, less of the predetermined flow capacity is available for storm water. Thus, the system becomes susceptible to rainfall amounts less than the planned certain rainfall amount causing numerous overflows into streams and lakes and backups into buildings through the service lines. Overflows also can occur in systems where the storm water is carried in a separate set of pipes. Such overflows and backups cause serious environmental and health problems.
Also, some sewer systems were designed with less capacity than is required to carry typical rainfall amounts thereby always overflowing during normal rainfalls. Typically, such systems were installed before there was much concern for the effect of the overflow on the environment.
However, no matter what the configuration of an existing sewer system, it either now has or will in the near future have flow capacity problems causing overflows, backups and leaks. Consequently, the local governments responsible for maintaining these sewer systems face enormous expenses to repair or replace the existing pipes and/or add capacity.